The Sky Between Us - Goh Kian Hui

Two Birds. Two Children. One Sky
Two birds are born a morning’s flight apart, on opposite sides of a border neither can name.
Each of them learns one human child: a girl who leaves water out every morning, a boy who waits, perfectly still, for a bird to come down and drink.
Then the war comes for both, on the same day, from opposite directions.
What the birds carry away is a pink thread and a yellow strand. Light enough to fly with. Strong enough to hold a nest together.